In the ongoing debate over whether Missouri should cut taxes, Republicans have argued that the sizable cut lawmakers are now considering will have little initial impact because it will be phased in over several years.

On Thursday, Attorney General Chris Koster took a meat clever to that argument.

In a legal opinion, his office said if certain “triggering events” occur, taxpayers “may seek refunds of taxes paid in the three preceding tax years.”

One of those triggering events is congressional passage of the Marketplace Fairness Act, which would enable states to collect sales taxes on Internet transactions.

Nixon, a fellow Democrat, has been talking about the possibility of costly retroactive refunds for weeks. In fact, he’s said that if the General Assembly overrides his veto of the big tax-cut bill next month, the initial cost to the state could be as much as $1.2 billion.

The opinion gives Nixon one more point to make as he continues his ongoing lobbying campaign against the tax cut. Nixon has visited about three dozen cities in recent weeks in a bid to stave off the override.

House Speaker Tim Jones took quick exception to Koster’s opinion, accusing the attorney general of siding with “the liberal, tax-and-spend views of the governor and the president.”